1. Field of the Invention
This invention relates to locks which allow a door to be partially opened without being unlocked. More particularly, this invention relates to a bar lock which allows a door to be partially opened while remaining locked and can be used as a lever to force the door closed.
2. Description of the Prior Art
The prior art includes numerous lock devices which permit a door to be partially opened while still remaining locked. Examples include structures ranging from the common chain lock to various sliding clasp locks.
U.S. Pat. No. 3,980,330 to Walker shows a device with a rotatable clasp on the door jamb which fits over and between a slidable bar on the door face. This safety latch will allow a door to be held in the lock position or in a partially opened position. This lock has 2 plates in which a sliding bolt is inserted. One plate holds the plate closed; the other plate will allow the door to be partially opened.
U.S. Pat. No. 3,924,885 to Markovitch is a safety latch with a rotatable clasp, which disengages from the hinge to allow the door to be opened. The latch in this invention is telescopic. A T-shaped engagement nose slides in a slot within a link. When the link is fully extended and the T-shaped nose is at the end of the link the door is held partially open but firmly locked.
U.S. Pat. No. 3,924,886 to Markovitch, discloses a safety latch with a rotatable clasp which is hinged in the middle and which comes apart in the middle of the clasp. A latch link and an intermediate link are folded into a base and slide to a non-engagement position. They may also be slid to a position where a latch link is engaged with a latch plate and the links can unfold to permit the door to open to a limited position.
U.S. Pat. No. 1,661,706 to Schobert et al., shows a clasp which fits in a grooved slide in a retainer on the door face.
The prior art fails to provide a simple lock device wherein a solid locking bar can be used to hold the door in a fully closed position, a partially open position, and also be used as a lever to help close the door against one who is attempting to force his way in.